In recent years, an all-solid battery where the electrolytic solution is replaced with a solid electrolyte is attracting attention. Compared with a secondary battery using an electrolytic solution, since the all-solid battery uses no electrolytic solution, the problems of decomposition of the electrolytic solution and the like do not arise. Furthermore, the all-solid battery has high cycle durability and high energy density.
The production method of such an all-solid battery generally involves processes of applying an active material slurry onto a current collector layer, drying or calcining the slurry to form a dried active material layer, applying a solid electrolyte slurry onto the dried active material layer, and drying or calcining the slurry. Accordingly, with respect to a laminate in which two or more layers using a slurry-like raw material layer are stacked, the method of the laminate includes two or more processes of drying the slurry-like raw material, and therefore, there is a problem that it is unavoidable to increase the number of processes and prolong the time needed for the production of the laminate. Resolution of such a problem has been sought for.
The production method of a secondary battery of Patent Document 1 (Japanese Unexamined Patent Publication No. 2010-113819) includes processes of lamination-coating a first current collector layer with a positive electrode active material slurry layer, a solid electrolyte slurry layer, and a negative electrode active material slurry layer without drying the layers, drying the slurry layers collectively, and overlaying a second current collector layer thereon. Patent Document 1 describes that with respect to this production method of a secondary battery, a high-capacity secondary battery can be manufactured with high productivity.
The production method of a lithium ion battery of Patent Document 2 (Japanese Unexamined Patent Publication No. 2013-127857) includes applying an active material-containing slurry onto a current collector and applying a slurry containing inorganic particles, etc., on the active material-containing slurry; and drying these slurries to form an active material layer on the current collector layer and form an electrolyte layer containing inorganic particles, etc. on the active material layer. Patent Document 2 describes that with respect to this production method of a lithium ion battery, a metallic foreign material with a possibility getting mixed in during a conventional plurality of processes can be prevented from getting mixed in and an internal short circuit can be suppressed.
The production method of an all-solid battery of Patent Document 3 (Japanese Unexamined Patent Publication No. 2015-008073) includes applying a solid electrolyte slurry onto a surface of a negative electrode active material layer and drying the slurry to manufacture a negative electrode body; applying a solid electrolyte slurry onto a surface of a positive electrode active material layer and drying the slurry to manufacture a positive electrode body; and laminating together the solid electrolyte layer side of the negative electrode body and the solid electrolyte layer side of the positive electrode body with heat and pressure. Patent document 3 describes that with respect to this production method of an all-solid battery, at least either one of the solid electrolyte layer of the negative electrode body and the solid electrolyte layer of the positive electrode body is a glass-based solid electrolyte.
Furthermore, the production method of an electrode for all-solid batteries of Patent Document 4 (Japanese Unexamined Patent Publication No. 2013-118143) includes kneading an active material, a solid electrolyte, a binder and a solvent to prepare a slurry-like electrode composition; applying the prepared slurry-like electrode composition; and drying the applied slurry-like electrode composition. Patent document 4 describes that with respect to this production method of an electrode for all-solid batteries, the solvent contains a good solvent for the binder and a poor solvent for the binder, and that the good solvent for the binder includes heptane and the poor solvent for the binder includes butyl butyrate.